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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id l26sm2077279oos.43.2020.05.21.16.35.56 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Thu, 21 May 2020 16:35:58 -0700 (PDT) Date: Thu, 21 May 2020 16:35:42 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Johannes Weiner cc: Hugh Dickins , Michal Hocko , Naresh Kamboju , Chris Down , Yafang Shao , Anders Roxell , "Linux F2FS DEV, Mailing List" , linux-ext4 , linux-block , Andrew Morton , open list , Linux-Next Mailing List , linux-mm , Arnd Bergmann , Andreas Dilger , Jaegeuk Kim , Theodore Ts'o , Chao Yu , Andrea Arcangeli , Matthew Wilcox , Chao Yu , lkft-triage@lists.linaro.org, Roman Gushchin , Cgroups Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page In-Reply-To: <20200521215855.GB815153@cmpxchg.org> Message-ID: References: <20200520190906.GA558281@chrisdown.name> <20200521095515.GK6462@dhcp22.suse.cz> <20200521105801.GL6462@dhcp22.suse.cz> <20200521124444.GP6462@dhcp22.suse.cz> <20200521191746.GB815980@cmpxchg.org> <20200521215855.GB815153@cmpxchg.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org On Thu, 21 May 2020, Johannes Weiner wrote: > On Thu, May 21, 2020 at 01:06:28PM -0700, Hugh Dickins wrote: > > On Thu, 21 May 2020, Johannes Weiner wrote: > > > do_memsw_account() used to be automatically false when the cgroup > > > controller was disabled. Now that it's replaced by > > > cgroup_memory_noswap, for which this isn't true, make the > > > mem_cgroup_disabled() checks explicit in the swap control API. > > > > > > [hannes@cmpxchg.org: use mem_cgroup_disabled() in all API functions] > > > Reported-by: Naresh Kamboju > > > Debugged-by: Hugh Dickins > > > Debugged-by: Michal Hocko > > > Signed-off-by: Johannes Weiner > > > --- > > > mm/memcontrol.c | 47 +++++++++++++++++++++++++++++++++++++++++------ > > > 1 file changed, 41 insertions(+), 6 deletions(-) > > > > I'm certainly not against a mem_cgroup_disabled() check in the only > > place that's been observed to need it, as a fixup to merge into your > > original patch; but this seems rather an over-reaction - and I'm a > > little surprised that setting mem_cgroup_disabled() doesn't just > > force cgroup_memory_noswap, saving repetitious checks elsewhere > > (perhaps there's a difficulty in that, I haven't looked). > > Fair enough, I changed it to set the flag at initialization time if > mem_cgroup_disabled(). I was never a fan of the old flags, where it > was never clear what was commandline, and what was internal runtime > state - do_swap_account? really_do_swap_account? But I think it's > straight-forward in this case now. > > > Historically, I think we've added mem_cgroup_disabled() checks > > (accessing a cacheline we'd rather avoid) where they're necessary, > > rather than at every "interface". > > To me that always seemed like bugs waiting to happen. Like this one! > > It's a jump label nowadays, so I've been liberal with these to avoid > subtle bugs. > > > And you seem to be in a very "goto out" mood today - we all have > > our "goto out" days, alternating with our "return 0" days :) > > :-) > > But I agree, best to keep this fixup self-contained and defer anything > else to separate cleanup patches. > > How about the below? It survives a swaptest with cgroup_disable=memory > for me. I like this version *a lot*, thank you. I got worried for a bit by the "#define cgroup_memory_noswap 1" when #ifndef CONFIG_MEMCG_SWAP, but now realize that fits perfectly. > > Hugh, I started with your patch, which is why I kept you as the > author, but as the patch now (and arguably the previous one) is > sufficiently different, I dropped that now. I hope that's okay. Absolutely okay, these are yours: I was a little uncomfortable to see me on the From line before, but it also seemed just too petty to insist that my name be removed. (By the way, off-topic for this particular issue, but advance warning that I hope to post a couple of patches to __read_swap_cache_async() before the end of the day, first being fixup to some of your mods - I suspect you got it working well enough, and intended to come back to check a few details later, but never quite got around to that.) > > --- > From d9e7ed15d1c9248a3fd99e35e82437549154dac7 Mon Sep 17 00:00:00 2001 > From: Johannes Weiner > Date: Thu, 21 May 2020 17:44:25 -0400 > Subject: [PATCH] mm: memcontrol: prepare swap controller setup for integration > fix > > Fix crash with cgroup_disable=memory: > > > > > > + mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8NRK0BPF6XF > > > > > mke2fs 1.43.8 (1-Jan-2018) > > > > > Creating filesystem with 244190646 4k blocks and 61054976 inodes > > > > > Filesystem UUID: 3bb1a285-2cb4-44b4-b6e8-62548f3ac620 > > > > > Superblock backups stored on blocks: > > > > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, > > > > > 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, > > > > > 102400000, 214990848 > > > > > Allocating group tables: 0/7453 done > > > > > Writing inode tables: 0/7453 done > > > > > Creating journal (262144 blocks): [ 35.502102] BUG: kernel NULL > > > > > pointer dereference, address: 000000c8 > > > > > [ 35.508372] #PF: supervisor read access in kernel mode > > > > > [ 35.513506] #PF: error_code(0x0000) - not-present page > > > > > [ 35.518638] *pde = 00000000 > > > > > [ 35.521514] Oops: 0000 [#1] SMP > > > > > [ 35.524652] CPU: 0 PID: 145 Comm: kswapd0 Not tainted > > > > > 5.7.0-rc6-next-20200519+ #1 > > > > > [ 35.532121] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS > > > > > 2.2 05/23/2018 > > > > > [ 35.539507] EIP: mem_cgroup_get_nr_swap_pages+0x28/0x60 > > Swap accounting used to be implied-disabled when the cgroup controller > was disabled. Restore that for the new cgroup_memory_noswap, so that > we bail out of this function instead of dereferencing a NULL memcg. > > Reported-by: Naresh Kamboju > Debugged-by: Hugh Dickins > Debugged-by: Michal Hocko > Signed-off-by: Johannes Weiner Acked-by: Hugh Dickins > --- > mm/memcontrol.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 3e000a316b59..e3b785d6e771 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -7075,7 +7075,11 @@ static struct cftype memsw_files[] = { > > static int __init mem_cgroup_swap_init(void) > { > - if (mem_cgroup_disabled() || cgroup_memory_noswap) > + /* No memory control -> no swap control */ > + if (mem_cgroup_disabled()) > + cgroup_memory_noswap = true; > + > + if (cgroup_memory_noswap) > return 0; > > WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files)); > -- > 2.26.2